First integrals for two linearly coupled nonlinear Duffing oscillators. Naz, R., Naeem, I., Mahomed, F.M. (2011) Mathematical Problems in Engineering
First order elliptic systems and the existence of homoclinic orbits in Hamiltonian systems. H. Hofer, K. Wysocki (1990) Mathematische Annalen
Frentes de explosión en ecuaciones de Hamilton Jacobi por argumentos de control determinista. G. Díaz (1989) Revista de la Real Academia de Ciencias Exactas Físicas y Naturales
Fundamental vector fields on type fibres of jet prolongations of tensor bundles Demeter Krupka (1979) Mathematica Slovaca